Formisano also faces two counts of second-degree possession of a weapon for an unlawful purpose and two counts of endangering the welfare of a child, prosecutors said in a news release. The estranged couple's two young children were in the family home when their mother was killed, authorities said.
Neither was injured.
CBS News reported that Formisano has been suspended without pay since the shooting. Newark Public Safety Director Anthony F. Ambrose released a statement in the wake of the killing.
"The Newark Public Safety Department is deeply saddened by the family tragedy involving Newark police Lt. John Formisano," Ambrose wrote. "Our foremost concern, of course, is for the couple's two children, who have lost their mother, and for the family of the victim.
"Lt. Formisano's colleagues in our police division were shocked by the news of the shooting and we recognize it this is a tragedy beyond comprehension for all involved."
The Morris County Prosecutor's Office said Monday that officers were called around 11:21 p.m. Sunday to 1 Mirror Place in response to a report of shots fired. When they arrived, they found Solaro dead on her neighbor's steps. The unidentified male victim was found with multiple gunshot wounds inside the Formisano home.
Neither police nor prosecutors mentioned the presence of the children, but police sources told NBC New York both children were home when the shooting took place. It was unclear what portion, if any, of the shootings they witnessed.
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A retired Passaic County sheriff's deputy who lives in the neighborhood said at least one neighbor witnessed the shooting, which began at the Formisano home at 1 Mirror Place.
"(The shooter) went in the front door," Thomas Verrone told NJ.com. "He shot the boyfriend three times and he shot the wife two times. She ran out of that house, went to the next door neighbor, banging on the door, yelling she had been shot. But it was late at night, so no one answered.
"He came out, followed her and she went to the other neighbor's house," Verrone said. "She opened the (screen) door and then he unloaded more on her (and) she fell there."
Morris County prosecutors said Tuesday that Solaro's body was found on the front steps of the home at 5 Mirror Place.
Public records show Formisano owns the home at 1 Mirror Place. His wife is identified in mortgage documentation as Christie Solaro.
Formisano's Facebook profile, which appears to have been removed since his arrest, indicated the couple married in 2010. Both his and his estranged wife's Facebook pages were filled with photos of their children, including a family Christmas photo taken in December.
Photos on Formisano's Facebook page include a May photo of the couple and their daughter that appears to mark the girl's first communion. A June photo shows their 3-year-old son preparing for his first day of preschool.
Multiple neighbors reported hearing the gunshots, though they didn’t know at the time what the sounds were.
"Heard the gunshots loud and clear last night," MaryAnn Mullane wrote on the Jefferson Township Police Department's Facebook page. "Thought it was someone setting off fireworks. So very heartbreaking."
"It's horrifying. It's scary," Liliana Morgan, a longtime resident, told the Daily Record. "It's not anything you expect."
Another neighbor who asked to remain anonymous described the community as a “sleepy town.”
A fourth neighbor, who also withheld her name, said she learned of the shooting -- and the identity of the accused -- around 12:30 a.m. Monday.
"He seemed normal," the woman told the newspaper. "Don't they always?"